#include <iostream>
#include <string>
#include <vector>
using namespace std;


class String{
  private:
    string str;
  public:
    string Z_shaping(int line, const string &str){
        if (line == 1){
            return str;
        }
        vector<string> rows(line);
        int index = 0;
        int step = 1;
        for (char c : str) {
            rows[index].push_back(c);
            if (index == 0) {
                step = 1;
            } else if (index == line - 1) {
                step = -1;
            }
            index += step;
        }
        string result;
        for (const string& row : rows) {
            result += row;
        }
        return result;
    }
};


int main(){
    String s;
    int line;
    string str;
    cin >> line;
    cin >> str;
    cout << s.Z_shaping(line, str) << endl;
    return 0;
}